Sharif Digital Repository

Amorphous SiBNC ceramics have been developed as new high temperature materials. They show a high resistance against crystallization, high mechanical properties, low density, and high oxidation stability. Three synthesis methods have been developed for synthesis of SiBNC ceramics namely, Reactive magnetron sputtering, Mechanical alloying plus sintering, and polymer-derived ceramics. In this research among polymeric methods one pot synthesis due to high ceramic yield and high mechanical properties have been chosen. Two major methods for nanofiber preparation are Meltspinning and Electrospinng. It is notable that all of researches for SiBNC Nanofiber preparation has been conducted on... 

In this study, standard composite laminate specimens with micro and nano sized particle additives are made to study the effect of the additives on the fracture toughness of the specimens in standard tests. The composite laminates are made from epoxy resin and unidirectional glass fibers. The mode I and mode II fracture toughness of the specimens are measured under various loadings in standard tests. The fracture surface is then, fractogaphed by microscopic instruments. In conclusion, the fracture behavior of laminated composites, toughened by micro and nano particles is discussed. The results show that using rubber particles will improve fracture toughness of neat epoxy resin and laminated... 

Since expansion of communication technology, telecommuting has gained attention from transportation planners as an approach in field of demand management. In this research, joint effects of feasibility of telecommuting for the employees of each organization and the relevant frequency of employees have been evaluated by using the copula model as the most recent conventional way of developing a joint model since the last few years. The result of telecommuting acceptance is that after presenting the project to each organization, the head employer measures the appropriateness of the project for employees and if he reaches a consensus on the success of the project, the employees get involved and... 

Nowadays, the inside needle capillary adsorption trap (INCAT) technique as a solventless sample preparation approach and alternative extraction method derived from SPME is gaining rising attentions. The INCAT and needle-trap devices are inexpensive, robust, reusable, and are applicable for sampling and analyzing suitable organic compounds from many different sample matrices. Compared to the fragile silica-based SPME fiber, the needle device is nearly impossible to break mechanically. In addition, the extraction medium possesses quite a large extraction phase volume and a powerful preconcentration capability. Similar to SPME, needle-like devices are particularly convenient for automation and... 

This project is aimed to design a controller for nonlinear systems that satisfy a prescribed performance while guaranteeing close-loop stability. To do this, the controller must be designed in such a way that the transient response of the system has had these performance indices and does not exceed them. These performance indices predefine some constraints for systems’ output.A comprehensive form for the model system, the unknown dynamics of the system, consideration of a variety of constraints on the system input, usage of the time-finite method for the residence time and consideration of just one tuning parameter to reduce the computation load, are among the other benefits for the proposed... 

The nickel-based superalloys play a key role in the development of aircraft and power-generation turbines due to their exceptional properties of high temperature strength, toughness, crack growth resistance and resistance to degradation corrosive and oxidisation environment.In this thesis, the role of base metal composition in isothermal solidification time during diffusion brazing of Nickel-based super alloys was investigated. To achieve this aim, four different super alloys Hynes230, Hastalloy X, Nimonic 263 and Monel were used in similar joining systems. Systems of H230/H230, HX/HX, C263/C263, and Monel/Monel were joined by BNi2 interlayer at 1323K and for different times, until the... 

Queue is crucial in new atmosphere of business. Firms and people see the dark side of this phenomenon. Investigation on The other side of queue is our main purpose of this study. Examining the relationship between queue and Perceived Quality, Price, Sacrifice, Value, and willingness to buy that make our conceptual framework and hypotheses is our primary objective.Questionnaire designed for evaluating construct. For each construct, standard scale was used. A survey was conducted in Iranian universities. The final sample includes 295 respondents. Regression analyses were performed.Results show significant relationship between our construct that confirm the other side of queue. Results show... 

In order to improve mechanical properties and increase the load capacity of soil so many different methods are innovated and utilized. Through This variety we can mention cement and asphalt concrete pavements which are the most common methods, cement sprinkling for consolidation of inclined surfaces and utilizing geotextiles and geomembranes which are recent methods. As far as a method becomes more common in industry, analytical study on effect of these methods on soil properties drew more attention in researches.In this research a homogenous elastic half-space is reinforced by an extensible thin plate and studied under various loads. The plate is considered as a buried infinite plane with... 

Solid-State Drives (SSDs) provide high performance, low power consumption, and hence are widely used in the I/O cache of enterprise storage systems and high performance servers. Although employing high performance SSDs in the I/O cache of storage systems significantly improves system performance, it comes with significant reliability threats for write operations upon power failures. In order to provide high level of reliability, storage architectures employ SSDs in I/O cache with RAID-1 configuration, however, such configuration only partially mitigates the reliability issues of the SSDs. In this thesis, we analyze the reliability of SSD-based I/O caches against power outage and high...